Various lancing devices are known for penetrating the skin of a human or animal subject at a lancing site for obtaining a sample of blood or other body fluids. In general, a typical lancing device includes a housing containing a lancet connected to a spring-driven drive mechanism, and further includes a cocking mechanism for arming or energizing the drive-spring, and a trigger mechanism for releasing the drive mechanism to complete the lancing operation. Many lancing devices further include a depth-control mechanism for varying the depth of penetration, either by adjusting the distance of travel of the lancet tip, or by adjusting the position of an endcap through which the lancet protrudes during the lancing operation.
The lancet is typically a disposable component that can be releasably mounted in a cooperating lancet carrier that is operatively coupled to the drive mechanism of the lancing device. The used lancet typically is removed from the lancet carrier after sampling and disposed of. A new, sterile lancet is then replaced into the lancet carrier for further sampling. Most known lancets comprise a metal needle or blade (collectively referred to herein as a “lancet blade”) with a sharp lancing tip. The lancet blade is typically embedded in a plastic body that has a size and shape configured for releasable engagement in the lancet carrier. The sharp tip of the lancet blade is typically embedded in a removable plastic shroud or cap to maintain sterility prior to use. Often, the endcap and the body of the lancet form a single, unitary plastic molding with a notched or necked section of reduced thickness for facilitating detachment and removal of the endcap.
Traditionally, a diabetic subject would use a lancing device to create a puncture wound in his/her skin at the desired sampling site, squeeze or “milk” the site to express a small sample droplet of blood, collect the sample droplet on a chemical test strip, insert the test strip in a blood glucose monitor for analysis, and review the test results. This procedure tends to be inconvenient and tedious, and the handling of small components may be difficult for subjects with impaired vision and manual dexterity. In order to encourage compliance with a prescribed sampling regimen, it is desirable to minimize the inconvenience resulting from the lancing procedure. Therefore, the market is tending to favor “all-in-one” devices that carry out the lancing, sample collection and sample analysis procedures in a single device.
Such all-in-one devices typically require precise alignment of the lancing site with the positioning of the sample collection media so that the user does not have to endure multiple lancet sticks or fumble with the test device to correct misalignments between the lancing site and the collection media. However, previously known lancing devices and lancets generally do not permit as precise control over the position of the lancing site as would be desired. This is often due to tolerance stacking resulting from slight variation in dimensions of the lancet blade, the plastic body of the lancet, the lancet carrier, the drive mechanism of the lancing device, the lancet housing, and/or other components, as well as the position of the lancet blade in the plastic body of the lancet. Individually, these dimensional variations may be small and within accepted manufacturing tolerances, but their aggregate effect sometimes results in a substantial misalignment of the lancing site and the location of the collection media delivered by an all-in-one sampling and test device. As a result, many all-in-one sampling and test devices are configured to generate a larger sample size than would otherwise be needed, in order to compensate for any such misalignments. However, generating a larger sample size typically requires that a larger wound be created during the lancing step, which adversely results in the infliction of more pain on the subject. Pain resulting from the lancing procedure often negatively affects patient compliance with a prescribed testing regimen, and is always sought to be minimized.
Accordingly, it can be seen that needs exist for devices and methods for enabling more precise guidance of a lancet, reducing tolerance stacking in the lancing procedure, and improving locational control of the of the puncture site. It is to the provision of devices and methods meeting this and other needs that the present invention is primarily directed.